In a conventional method and a conventional apparatus such as those disclosed in the Japanese Patent Publication No. 10544/80, the Japanese Patent Publication No. 10545/80, the Japanese Patent Application (OPI) No. 92524/82 (the term "OPI" as used herein means an "unexamined published application") and the Japanese Utility Model Application (OPI) No. 117834/85 for manufacturing silver halide grains, a water-soluble silver salt solution and a water-soluble halide solution are put into a mixing chamber in a reaction vessel and quickly stirred and mixed together to react with each other to produce the silver halide grains and disperse crystallates to age the grains.
However, the larger the capacity of the reaction vessel is, the more difficult it is to mix the solutions uniformly in the reaction vessel. For that reason, the silver halide grains can have a different crystal appearance, grain distribution or the like from those desired.